TCP Wrappers Release Notes

Known Problems and Limitations
Limitations
Chapter 4 25
Limitations
The following are the limitations in this release of TCP Wrappers:
• When a new request comes in, the UDP (rpc/udp) daemons linger
around for a while after servicing the request.In the /etc/inetd.conf
file, these daemons are registered with the ‘wait’ option. The nowait
option is not supported. Only the request which started such a
daemon will be seen by the wrappers.
• The wrappers do not work with RPC services over TCP. These
services are registered as rpc/tcp in the /etc/inetd.conf file. The only
non-trivial service that is affected by this limitation is rexd, which is
used by the on(1) command.
• Some RPC requests like rwall, rup, rusers et al appear to come from
the server host. The client broadcasts its request to all portmap
daemons on its network; each portmap daemon in turn forwards the
request to a daemon on its own system. However, daemon like rwall
assumes that the request is coming from the local host.
• The user name lookup feature of TCP Wrappers uses identd to
identify the username of the remote host. By default, this feature is
disabled, as identd may appear hung when there are large number of
TCP connections. To enable the username lookup, perform the steps
as described in the tcpd.conf(4)man page.